1. Field of the Invention
The present invention generally relates to a communication system, and more particularly to a system and method for transmitting resource allocation information in a wireless communication system.
2. Description of the Related Art
Extensive research is being conducted to provide users with high-speed services based on various Qualities of Service (QoSs) in fourth-generation (4G) communication systems serving as next-generation communication systems. Specifically, active research is being conducted to support high-speed services for ensuring mobility and QoS in Broadband Wireless Access (BWA) communication systems such as Wireless Local Area Network (WLAN) and Metropolitan Area Network (MAN) communication systems in the current 4G-communication systems.
A transmitter and receivers of the above-described wireless communication system, i.e., a Base Station (BS) and Mobile Station (MS), employ a frame structure to exchange data. When the communication system employs the frame structure for a data transmission between the transmitter and the receiver, i.e., the BS and the MS, the BS efficiently allocates resources of frames to the MS such that they can use the resources. Resource allocation information is sent to the MS through a MAP message. Herein, a MAP message for transmitting downlink (DL) resource allocation information is a DL-MAP message and a MAP message for transmitting uplink (UL) resource allocation information is a UL-MAP message.
When the BS transmits DL and UL resource allocation information in the DL and UL MAP messages, the MSs decode the DL and UL MAP messages transmitted from the BS, such that they can detect positions of their own allocated resources and control information on their own received data. The MSs can receive or transmit data through a DL or UL by detecting the resource allocation positions and the control information.
FIG. 1 illustrates the resource domain of the conventional wireless communication system.
Referring to FIG. 1, the resource domain includes MAP messages for transmitting resource allocation information and data mapped to the MAP messages. A first MAP message includes resource allocation information mapped to first data, a second MAP message includes resource allocation information mapped to second data, and a third MAP message includes resource allocation information mapped to third data.
The BS transmits MAP messages containing resource allocation information and allocated resources together. When receiving the MAP message, the MS decodes the MAP message and detects positions of its own allocated resources and control information, thereby receiving its own allocated data.
FIG. 2 illustrates a resource allocation information transmission/reception in the conventional wireless communication system.
As illustrated in FIG. 2, a plurality of resource allocation information regions are, for example, a first MAP message 200, a second MAP message 230, and a third MAP message 260, and a plurality of data, namely, first data 210, second data 240, and third data 270 mapped to the MAP messages included in the resource allocation information regions. When the BS transmits MAP information mapped to the data 210, 240, 270 using the first, second, and third MAP messages 200, 230, and 260, the MS decode the MAP messages 200, 230, and 260 and detect MAP Information Elements (IEs) corresponding to information about their own allocated resources, thereby detecting their own allocated regions.
Herein, the IEs included in the MAP messages include their start points and sizes of regions allocated for the MS in time and frequency domains. When receiving the MAP messages, the MS decode the MAP messages and detect IEs, i.e., MAP IEs, indicative of information about their own allocated resources, thereby detecting positions of their own allocated resources.
When the MS detect their own allocated MAP IEs while sequentially decoding the MAP IEs included in the MAP messages, they learn positions of their own allocated resources using position information of the detected MAP IEs.
When receiving the MAP messages 200, 230, and 260 from the BS, the MS sequentially decodes the received first MAP message 200 and detects a MAP IE included in the first MAP message 200. The MS learns a position of its own allocated resources, i.e., a position of the first data 210, using position information of the detected MAP IE. Then, the MS receives the first data 210 allocated thereto.
When receiving the second MAP message 230 subsequent to the first MAP message 210 from the BS, the MS sequentially decodes the received second MAP message 230 and detects a MAP IE included in the second MAP message 230. The MS learns a position of its own allocated resources, i.e., a position of the second data 240, using position information of the detected MAP IE. Herein, the MS receives the second data 240 allocated thereto.
When receiving the third MAP message 260 subsequent to the first and second MAP messages 210 and 230 from the BS, the MS sequentially decodes the received third MAP message 260 and detects a MAP IE included in the third MAP message 260. The MS learns a position of its own allocated resources, i.e., a position of the third data 270, using position information of the detected MAP IE. Herein, the MS receives its own allocated third data 270.
As described above, the BS transmits resource allocation information through the first, second and third MAP messages 200, 230, and 260, and transmits data allocated to the MS using the MAP messages. Each MS decodes a MAP message and receives its own allocated data.
The BS transmits resource allocation information to all MSs for receiving a service from the BS in a frame. Thus, the resource allocation information is broadcast to the MS located within a cell of the BS. It is important that the MS receive the resource allocation information because the BS and the MS transmit and receive data using the resource allocation information. However, the current wireless communication system is sensitive to interference, multipath fading and thermal noise due to characteristics of a radio channel in which data is sent. When the resource allocation information, i.e., the MAP message, which is more robust than data is sent, a Modulation and Coding Scheme (MCS) at a low transmission rate according to channel characteristics is used. Specifically, when the MAP message is sent, the MCS is used at a low transmission rate like Quadrature Phase Shift Keying (QPSK) 1/12 or ⅛. When data is sent at the low transmission rate, error in a data transmission and reception is reduced. The reliability of a MAP message transmission and reception relative to MS within a cell increases.
However, the resource allocation information such as the MAP message is a type of overhead information for transmitting data from the BS to the MS. When the MAP message is sent through the MCS at a low rate, a waste of resources occurs.
The MAP messages corresponding to the resource allocation information of the wireless communication system are broadcast to all MS located in a cell covered by the BS. Hence, a problem occurs in that the MAP message size increases and the throughput of the overall system is degraded according to MAP message size when the number of MS increases.